<?php
/**
 * PHPExcel
 *
 * Copyright (c) 2006 - 2011 PHPExcel
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * @category   PHPExcel
 * @package    PHPExcel_Shared_Best_Fit
 * @copyright  Copyright (c) 2006 - 2011 PHPExcel (http://www.codeplex.com/PHPExcel)
 * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
 * @version    1.7.6, 2011-02-27
 */


require_once(PHPEXCEL_ROOT . 'PHPExcel/Shared/trend/bestFitClass.php');


/**
 * PHPExcel_Linear_Best_Fit
 *
 * @category   PHPExcel
 * @package    PHPExcel_Shared_Best_Fit
 * @copyright  Copyright (c) 2006 - 2011 PHPExcel (http://www.codeplex.com/PHPExcel)
 */
class PHPExcel_Linear_Best_Fit extends PHPExcel_Best_Fit
{
    protected $_bestFitType        = 'linear';


    public function getValueOfYForX($xValue) {
        return $this->getIntersect() + $this->getSlope() * $xValue;
    }    //    function getValueOfYForX()


    public function getValueOfXForY($yValue) {
        return ($yValue - $this->getIntersect()) / $this->getSlope();
    }    //    function getValueOfXForY()


    public function getEquation($dp=0) {
        $slope = $this->getSlope($dp);
        $intersect = $this->getIntersect($dp);

        return 'Y = '.$intersect.' + '.$slope.' * X';
    }    //    function getEquation()


    private function _linear_regression($yValues, $xValues, $const) {
        $this->_leastSquareFit($yValues, $xValues,$const);
    }    //    function _linear_regression()


    function __construct($yValues, $xValues=array(), $const=True) {
        if (parent::__construct($yValues, $xValues) !== False) {
            $this->_linear_regression($yValues, $xValues, $const);
        }
    }    //    function __construct()

}    //    class linearBestFit